Persistent Infections: Etiology

Most cases of apical periodontitis (75 to 90 %) react positively to endodontic treatment with complete healing as a result. However, in some cases the infection continues (but may be symptom-free) and healing of the bone lesion is not obtained. There may be several causes; often problems in finding and cleaning all areas of the complex root canal system are causes of reason for failure. Sometimes the infective flora may be unusually resistant to normal chemomechanical treatment and local disinfecting agents, or the infection may be be inaccessible to conservative treatment (e.g. periapical actinomycosis).